Hear us out.

As the days of suburban sprawl give way to those of urban density in U.S. metros–“smart growth,” most call it–providing sufficient housing remains a challenge. Decades of planning regulations and highway patterns support single-family homes built far outside a city center. Even in areas where big residential towers make sense, developing them takes a long time and costs a lot of money. Manhattan wasn’t built in a day.

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The premise that single-family house neighborhoods should be frozen in amber is increasingly being questioned.

Planning scholar Jake Wegmann, who’s in the process of moving from Berkeley to the University of Texas at Austin, believes there’s another way: backyard cottages. Hear him out. Individual micro-units on single-family properties don’t require much time or money to build. They don’t need much space to sit on. They’re affordable almost by definition and are well-suited to the modern family–from the recent college grad living at home to the grandparent who wants to age in place.

In other words, backyard cottages may not scream Manhattanization or even necessarily smart growth, but implemented over a wide swatch of a metro area they might achieve a similar end. Their potential seems even greater in places trying to reduce their reliance on cars and promote access to shops by walking or public transit. At the very least, Wegmann believes, cottages should be part of the broader conversation about the changing shape of American cities.

“The premise that single-family house neighborhoods are, or should be, frozen in amber is increasingly being questioned,” he tells Co.Design.

One place ripe for such development in Wegmman’s mind is the East Bay, an area just across the water from San Francisco that includes parts of Berkeley, Oakland, and El Cerrito. Housing demand is enormous in the Bay Area, but the city itself has become largely unaffordable. Still, the East Bay has strong transit access and clear walkable districts and enough density–at 11,700 people per square mile–to facilitate a more urbanized growth pattern.

Recently, Wegmann and Berkeley colleague Karen Chapple evaluated what life in the East Bay might look like in two different growth scenarios. The first, based on a conventional infill strategy of buildings with five or more units located around transit hubs, had the potential to add roughly 7,900 housing units to the area. They estimate that, given the recent pace of area development, building that much housing would take anywhere from 18 to 43 years.

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Next they looked at backyard cottages. Assuming a slight relaxation of zoning regulations from the present–a shift in keeping with California’s broader sustainability goals–the East Bay could accommodate nearly 8,700 cottages, Wegmann and Chapple report in the Journal of Urbanism. That’s not only more than the conventional infill estimate but roughly 60% of the area’s total housing goal by 2040.

The concept goes well beyond the theoretical realm of academia. East Bay-based New Avenue specializes in helping single-family homeowners develop backyard cottages or “accessory dwellings.” (The company–billing itself as Uber for contractors–connects clients with architects and developers in an online forum while vetting project costs and timelines.) Founder Kevin Casey says zoning laws that once prevented this type of development are quickly changing to encourage it.

The Bay Area is the most expensive real estate in the market. By default, it’s the most logical place to do this.

“Anywhere there’s a growing economy and expensive housing, it makes sense,” Casey tells Co.Design. “The Bay Area is the most expensive real estate in the market, so it’s by default the most logical place to do this.” (Wegmann and Casey knew one another at Berkeley and remain acquainted, but Wegmann claims no financial interest in the company.)

Casey says a backyard cottage takes about six months to build after permitting (which can take anywhere from no time to a year). The costs vary but generally fall within a range of $80,000 to $250,000. Casey estimates that 82% of his clients have family members in mind for the dwelling; some see the cottages as a good starter home for when their children move back to the area, or a good retirement home for themselves down the line, or maybe both.

The view of backyard cottages as a family safety net raises the question of whether they’ll truly inspire homeowners to drop the isolated mindset that challenges urban density in the first place. Zoning and local politics might prove bigger hurdles. Smart growth has vehement opponents, and NIMBYs who see cottages as a threat to single-family neighborhoods might do their best to block new regulations, too. Financing problems also linger, especially since cottages don’t receive mortgage advantages given to income-based developments.

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The law needs to evolve to reflect changing attitudes.

Wegmann remains hopeful that backyard cottages can at least augment, though certainly not replace, the conventional infill strategy of big apartment buildings.

“My prediction is that we will continue to have structures that we today call ‘single-family houses’ for centuries to come, but that increasing numbers of them won’t be occupied by single families, and eventually the law will evolve to reflect changing attitudes,” he says. “Some of them will sprout cottages in their backyards. Of course, these changes won’t happen overnight.”

About the author

Eric Jaffe is an editor at CityLab, where he writes about transportation, history, and behavioral science, among other topics, through the lens of urban life. He's also the author of The King's Best Highway (2010) and A Curious Madness (2014).